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Ch.3 - Molecules, Compounds & Chemical Equations
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoTro 4th EditionCh.3 - Molecules, Compounds & Chemical EquationsProblema 131
Capitolo 3, Problema 131

Combustion analysis of a 13.42-g sample of equilin (which contains only carbon, hydrogen, and oxygen) produces 39.61 g CO2 and 9.01 g H2O. The molar mass of equilin is 268.34 g/mol. Find its molecular formula.

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Calculate the moles of CO2 produced using its molar mass: \( \text{moles of CO}_2 = \frac{39.61 \text{ g}}{44.01 \text{ g/mol}} \).
Determine the moles of carbon in the sample from the moles of CO2, knowing that each mole of CO2 contains one mole of carbon.
Calculate the moles of H2O produced using its molar mass: \( \text{moles of H}_2\text{O} = \frac{9.01 \text{ g}}{18.02 \text{ g/mol}} \).
Determine the moles of hydrogen in the sample from the moles of H2O, knowing that each mole of H2O contains two moles of hydrogen.
Calculate the mass of carbon and hydrogen in the sample, subtract from the total mass to find the mass of oxygen, and then determine the moles of oxygen.

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Combustion Analysis

Combustion analysis is a technique used to determine the elemental composition of organic compounds. In this process, a sample is burned in excess oxygen, producing carbon dioxide and water. The masses of these products are measured, allowing for the calculation of the amounts of carbon, hydrogen, and oxygen in the original sample.
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01:29
Combustion of Non-Hydrocarbons

Empirical Formula

The empirical formula represents the simplest whole-number ratio of the elements in a compound. To find it, the moles of each element are calculated from the combustion products, and then the ratios are simplified. This formula is crucial for determining the molecular formula when combined with the molar mass of the compound.
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02:26
Empirical vs Molecular Formula

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by multiplying it by a whole number, which is determined by dividing the compound's molar mass by the molar mass of the empirical formula. This provides insight into the compound's structure and properties.
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02:08
Determining Molecular Formulas
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Domanda del libro di testo

Epsom salts is a hydrated ionic compound with the following formula: MgSO4 • x H2O. A 4.93-g sample of Epsom salts is heated to drive off the water of hydration. The mass of the sample after complete dehydration is 2.41 g. Find the number of waters of hydration (x) in Epsom salts.

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Domanda del libro di testo

A hydrate of copper(II) chloride has the following formula: CuCl2 • x H2O. The water in a 3.41-g sample of the hydrate is driven off by heating. The remaining sample has a mass of 2.69 g. Find the number of waters of hydration (x) in the hydrate.

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Domanda del libro di testo

Fructose is a common sugar found in fruit. Elemental analysis of fructose gives the following mass percent composition: C 40.00%, H 6.72%, O 53.28%. The molar mass of fructose is 180.16 g/mol. Find the molecular formula of fructose.

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Domanda del libro di testo

Estrone, which contains only carbon, hydrogen, and oxygen, is a female sexual hormone in the urine of pregnant women. Combustion analysis of a 1.893-g sample of estrone produces 5.545 g of CO2 and 1.388 g H2O. The molar mass of estrone is 270.36 g/mol. Find its molecular formula.

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Domanda del libro di testo

A metal (M) forms an oxide with the formula M2O. If the oxide contains 16.99% O by mass, what is the identity of the metal?

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